US4689128A - Method of separating isotopes - Google Patents

Method of separating isotopes Download PDF

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Publication number
US4689128A
US4689128A US06/736,975 US73697585A US4689128A US 4689128 A US4689128 A US 4689128A US 73697585 A US73697585 A US 73697585A US 4689128 A US4689128 A US 4689128A
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isotope
laser
atom
laser light
isotopes
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Takashi Arisawa
Youji Suzuki
Yoichiro Maruyama
Masaaki Kato
Koreyuki Shiba
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Japan Atomic Energy Agency
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Japan Atomic Energy Research Institute
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D59/00—Separation of different isotopes of the same chemical element
    • B01D59/34—Separation by photochemical methods

Definitions

  • the present invention relates to a method of separating isotopes. More particularly, the invention relates to a method of separating a specific isotope from a mixture of isotopes by first irradiating the isotope mixture with a highly monochromatic laser light that resonates only with the energy level of the specific isotope so as to increase its chemical activity and then bombarding said specific isotope with a molecule containing highly reactive atoms so as to form a compound rich in the specific isotope.
  • the conventional technique for attaining this object is to ionize only the excited atoms with a light having a suitable wavelength and to collect them in an electric or magnetic field.
  • This technique generally referred to as the photoionization method, requires a laser of high power (for multiple-photon ionization) or more than one laser (for multi-stage ionization).
  • the photoionization method is hereunder described in detail with particular reference to the separation of uranium, lithium, calcium, rubidium or lanthanum isotopes.
  • a mixture of isotopes is irradiated with a laser light that resonates only with the energy level of the target isotope.
  • the target isotope absorbs the laser light and is subsequently irradiated with a laser light from the same or a different source.
  • ions are generated by photo-ionization of the target isotope and subsequently recovered by physical means.
  • exchange of electric charges occurs between the ions of the target isotope and the other neutral isotopes, and as a result, the number of ions derived from the target isotope is decreased whereas the number of ions derived from the unwanted isotopes is increased, and this leads to lower yields and separation factors.
  • the cross section of an atom for ionization is smaller than that for excitation by a factor of 10 3 to 10 4 . Therefore, there is a significant difference in transition probability between excitation from the ground state to the first stage of excitation and from the first stage to the second stage of excitation due to ionization.
  • the light source for photoionization In order to achieve efficient two-stage ionization, the light source for photoionization must have an intensity 10 3 to 10 4 times greater than that of the laser light for the first stage of excitation (selective excitation). Ionization involves an excitation to the continuous energy state and requires a laser of high power although this does not need high monochromaticity.
  • the first photon has a frequency that selectively excites the target isotope
  • the second photon has a frequency that boosts the same isotope to an upper excited state
  • the third photon has a frequency high enought to ionize said excited isotope. Therefore, three visible lasers are required, and the overall system including pumping sources and control devices becomes correspondingly complicated.
  • the present invention separates isotopes by a "selective chemical reaction" wherein a selective isotope in the excited stage enters selectively into a chemical reaction to form an easily separable compound.
  • a selective chemical reaction wherein a selective isotope in the excited stage enters selectively into a chemical reaction to form an easily separable compound.
  • one object of the present invention is to provide a method of separating isotopes.
  • Another object of the present invention is to provide a method of separating a specific isotope from an isotope mixture by exciting the specific isotope with a laser light and reacting said isotope with a molecule having a highly reactive atom so as to form a spatially separated compound rich in the specific isotope.
  • a further object of the present invention is to provide a method of separating a specific isotope from a mixture of isotopes by first irradiating a beam of the isotope mixture with a highly monochromatic laser light that resonates only with the energy level of the specific isotope so as to increase its chemical activity through absorption of the laser light and then bombarding it with a molecule containing a highly reactive atom so as to form a spatially separated compound rich in the specific isotope.
  • FIG. 1 is a schematic top view of the reactor that is used in one embodiment of the method of the present invention.
  • FIG. 1A is a perspective cross-section of the reactor of FIG. 1, taken along line 1--1.
  • FIG. 2 is a graph showing the distribution of scattering angles for the reaction product obtained by separating a specific lithium isotope by the method of the present invention.
  • a specific isotope is separated from a mixture of isotopes by first irradiating the isotope mixture with a highly monochromatic laser light which resonates only with the energy level of the specific isotope so as to increase its chemical activity through absorption of the laser light, and then bombarding it with a molecule containing a highly reactive atom so as to form a spatially separated compound rich in the specific isotope.
  • the most characteristic feature of the present invention lies in the means for separating a specific isotope that has been selectively excited by laser light.
  • the excited isotope is reacted with a molecule containing an atom such as a halogen that has selective reactivity with that isotope to form a spatially separated compound.
  • molecule as used above includes a radical generated from the molecule containing an atom that has selective reactivity with the excited isotope. Therefore, the method of the present invention is suitable for industrial application without requiring a powerful excitation or ionization laser, or a multiple-wavelength visible laser or pump laser as in the case of three-stage photoionization.
  • This apparatus consists of a vacuum chamber 2 which contains a crucible loaded with a metallic vapor source 3 containing the target isotope.
  • the metal 3 in the crucible becomes molten by resistance heating or electron bombardment, and the resulting metal vapor is collimated by a collimator 4 to form a metal vapor beam 5 which is directed upward.
  • the beam 5 is irradiated with a laser beam from a laser 1 preferentially exciting particles 9 of the selected isotope.
  • a beam of reactive gas emitted from a reactive molecule source 6 crosses the irradiated portion of the vapor beam so as to form a compound 8 which is deposited on a substrate 7.
  • the compound can be recovered as the final product by scrapping it from the substrate.
  • the compound rich in the target isotope produced by reacting said isotope in the excited state with a reactive molecule can be spatially separated by making use of the fact that said compound has a certain distribution of scattering angles with respect to the direction of the metallic vapor beam.
  • Lasers that can be used in the method of the present invention include dye lasers pumped by gas lasers such as Ar lasers, N 2 lasers, He-Cd lasers, solid-state lasers such as Nd-YAG lasers and metallic Cu lasers, and excimer lasers. As is known, these laser systems produce light in the visible spectrum. Also usable is the light that is emitted from these lasers and which is subjected to wavelength conversion with crystals, liquids or gasses, followed by processing with optical devices to provide higher monochromaticity.
  • gas lasers such as Ar lasers, N 2 lasers, He-Cd lasers, solid-state lasers such as Nd-YAG lasers and metallic Cu lasers, and excimer lasers.
  • these laser systems produce light in the visible spectrum. Also usable is the light that is emitted from these lasers and which is subjected to wavelength conversion with crystals, liquids or gasses, followed by processing with optical devices to provide higher monochromaticity.
  • a mixture of lithium isotopes containing the target species 6 Li was loaded into a crucible and heated by electron bombardment to form an atomic vapor.
  • the vapor was passed through a collimator to form a beam having a fairly high directionality.
  • the target isotope 6 Li was selectively excited by photons having a wavelength of 6708 ⁇ , but the other species and those 6 Li atoms not excited by the laser light remained in the ground state.
  • the excited atoms were then bombarded with a beam of CHClF 2 gas, whereupon LiCl and LiF were produced as the two reaction products in much higher yields than in the absence of irradiation with the laser light. This process involved the following two reactions:
  • LiF was more 6 Li-rich than LiCl.
  • the compound 6 LiF has a tendency to move in a direction that deviates from the atomic metal vapor and hence can be spatially separated from the isotope mixture.
  • -- -- -- refers to the amount of 7 LiF produced
  • -- ⁇ -- ⁇ -- refers to the amount of 6 LiF produced
  • -- refers to the content of 6 Li species in each end compound.
  • CHClF 2 was used as a molecule containing atoms having high reactivity with the target isotope, but it should be understood that reactive molecules containing a halogen atom may also be used, and such molecules include CCl 2 F 2 , CHF 3 , CCl 2 FH, CCl 4 , CF 4 , CF 3 I and CF 3 Br.
  • the method of the present invention can also be used to separate other isotopic atoms such as uranium. According to the present invention, a compound containing only a specific isotope can be directly produced. Since many isotopes are commonly used not in their elemental forms but as labeled compounds, this advantage of the present invention will contribute to an expanded use of lasers in separation of isotopes.

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  • Life Sciences & Earth Sciences (AREA)
  • Biophysics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Lasers (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
US06/736,975 1982-09-14 1985-05-22 Method of separating isotopes Expired - Fee Related US4689128A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP57-160537 1982-09-14
JP57160537A JPS5949826A (ja) 1982-09-14 1982-09-14 同位体の分離方法

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US06529508 Continuation 1983-09-06

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11276508B2 (en) 2018-12-20 2022-03-15 Battelle Energy Alliance, Llc Surrogate isotope-containing materials for emergency response training and Methods of formation and dispersal

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2025057616A1 (ja) * 2023-09-14 2025-03-20 国立大学法人大阪大学 原子濃縮装置、原子濃縮システム及び原子濃縮方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4176024A (en) * 1975-07-28 1979-11-27 Westinghouse Electric Corp. Gas dynamic reaction process and system for laser chemistry
US4187157A (en) * 1974-09-10 1980-02-05 Kraftwerk Union Aktiengesellschaft Method and apparatus for isotope concentration
US4327288A (en) * 1980-09-29 1982-04-27 Bell Telephone Laboratories, Incorporated Method for focusing neutral atoms, molecules and ions
US4386274A (en) * 1980-11-10 1983-05-31 Saul Altshuler Isotope separation by standing waves
US4514363A (en) * 1980-05-02 1985-04-30 The United States Of America As Represented By The United States Department Of Energy Method for isotope enrichment by photoinduced chemiionization

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4035270A (en) * 1975-04-23 1977-07-12 Exxon Research And Engineering Company Isotope separation process
US4255404A (en) * 1977-12-22 1981-03-10 Westinghouse Electric Corp. Isotopic separation

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4187157A (en) * 1974-09-10 1980-02-05 Kraftwerk Union Aktiengesellschaft Method and apparatus for isotope concentration
US4176024A (en) * 1975-07-28 1979-11-27 Westinghouse Electric Corp. Gas dynamic reaction process and system for laser chemistry
US4514363A (en) * 1980-05-02 1985-04-30 The United States Of America As Represented By The United States Department Of Energy Method for isotope enrichment by photoinduced chemiionization
US4327288A (en) * 1980-09-29 1982-04-27 Bell Telephone Laboratories, Incorporated Method for focusing neutral atoms, molecules and ions
US4386274A (en) * 1980-11-10 1983-05-31 Saul Altshuler Isotope separation by standing waves

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Isotope Separation by Laser Enhanced Chemical Reaction, Chemical Physics 81 (1983), 473 479; Takashi Arisawa, et al. *
Isotope Separation by Laser-Enhanced Chemical Reaction, Chemical Physics 81 (1983), 473-479; Takashi Arisawa, et al.

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11276508B2 (en) 2018-12-20 2022-03-15 Battelle Energy Alliance, Llc Surrogate isotope-containing materials for emergency response training and Methods of formation and dispersal

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JPS5949826A (ja) 1984-03-22
JPH0144371B2 (enrdf_load_stackoverflow) 1989-09-27

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